Undisturbed core sampler

ABSTRACT

A core sampler that complies with European Standard BS EN ISO 22457-1 and takes Class 1 samples, while being able to withstand forces associated with sonic drilling. The core sampler includes a smaller diameter, thin-walled sampler shoe portion that transitions to a larger diameter, thick-walled tube at a specific distance along the longitudinal axis of the core sampler. The smaller diameter shoe portion allows for an undisturbed sample, while the larger diameter tube imparts sufficient strength to the core sampler such that the core sampler can handle forces associated with sonic drilling techniques. Optionally, the larger diameter tube can provide the thickness needed for a liner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/475,506, which was filed on Apr. 14, 2011, which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field

Implementations of the present invention relate generally to drilling devices and methods that may be used to drill and take core samples from naturally occurring and/or manmade geological formations. In particular, implementations of the present invention relate to core samplers.

2. The Relevant Technology

Core drilling (or core sampling) includes obtaining core samples of subterranean formations at various depths for various reasons. For example, a retrieved core sample can indicate what materials, such as petroleum, precious metals, and other desirable materials, are present or are likely to be present in a particular formation, and at what depths such materials are present. In some cases, core sampling can be used to give a geological timeline of materials and events. As such, core sampling may be used to determine the desirability of further exploration in a particular area.

The quality of a core sample can be influenced by the tools used to obtain the sample, the drilling or sampling method, and the handling, transport, and storage of the sample. For some conventional forms of sample analysis, it is often desirable to have undisturbed samples. Mechanical disturbance of the soil during core sampling can affect the quality of a core sample. In particular, the smaller the “area ratio,” e.g., the ratio of area of soil displaced by the sampler in proportion to the area of the obtained sample, the more undisturbed the core sample will be. Unfortunately, the current industry trends typically include the use of thick walled tubes for core sampling. Such thick-walled tubes can have area ratios as high as 50%, which can cause undesirable disturbance of core samples.

European Standard BS EN ISO 22457-1 (herein, the “Standard”) defines five classes of sample quality. Class 1 includes the least “disturbed” samples. The Standard sets out that only Class 1 samples can be used for strength and compressibility testing. The Standard stipulates in part that samplers for obtaining Class 1 samples should be thin walled with a maximum area ratio of fifteen percent and a maximum cutting shoe taper of five degrees.

While a sampler meeting the requirements of the Standard may be capable of obtaining Class 1 samples, there is no guarantee that such a sampler will necessarily obtain Class 1 samples. Furthermore, it is possible that core samplers that comply with the Standard may not be robust enough to withstand harder and/or stony soils without incurring significant damage during the application of the forces required to advance the sampler, such as, for example, when using dynamic percussion hammers or sonic drilling techniques.

Accordingly, there is a need in the pertinent art for a core sampler that addresses the issues discussed above. More particularly, there is a need in the pertinent art for a core sampler that is capable of obtaining high-quality soil samples and that is robust enough to withstand advancement within hard and/or stony soils.

SUMMARY

Described herein is a core sampler that overcomes one or more problems in the art with drilling tools, systems, and methods for effectively and efficiently obtaining core samples. An exemplary core sampler as described herein complies with the European Standard BS EN ISO 22457-1 and takes high quality, undisturbed samples, while being able to withstand significant drilling forces associated with driving or hammering of the sampler and/or advancement of the core sampler within harder formations. In particular, the core sampler can include a smaller diameter, thinner walled shoe portion that transitions to a larger diameter, thicker walled tube portion at a predetermined, specific distance along a longitudinal axis of the core sampler. The smaller diameter shoe portion can allow for an undisturbed sample, while the larger diameter tube portion advantageously can impart increased strength to the core sampler. Additionally, it is contemplated that the larger diameter tube portion can provide the thickness needed for a liner, which allows the core sampler to be reusable.

Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates a perspective view of an exemplary core sampler as described herein;

FIG. 2 illustrates a perspective cross-sectional view of the core sampler of FIG. 1;

FIG. 3 illustrates another cross-sectional view of the core sampler of FIG. 1;

FIG. 4 illustrates an enlarged cross-sectional view of an exemplary shoe portion of the core sampler of FIG. 1;

FIG. 5 illustrates another enlarged cross-sectional view of an exemplary shoe portion of the core sampler of FIG. 1;

FIG. 6 illustrates another cross-sectional view of an exemplary core sampler as described herein; and

FIG. 7 illustrates a schematic diagram of an exemplary drilling system incorporating a core sampler as described herein.

DETAILED DESCRIPTION

The present invention may be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

The present invention can be understood more readily by reference to the following detailed description, examples, drawing, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

The following description of the invention is provided as an enabling teaching of the invention in its best, currently known embodiment. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof.

As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an opening” can include two or more such openings unless the context indicates otherwise.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

The present invention may be understood more readily by reference to the following detailed description of the invention and the examples included therein and to the Figures and their previous and following description.

Described herein are core samplers, systems, and methods for effectively and efficiently obtaining core samples. In one aspect, a core sampler as described herein can comply with the European Standard BS EN ISO 22457-1 and can be configured to take high quality, undisturbed samples while withstanding significant drilling forces associated with driving or hammering of the sampler and/or with harder formations. In one aspect, an exemplary core sampler can include a smaller diameter, thin-walled shoe portion that transitions to a larger diameter, thick-walled tube portion at a predetermined, specific distance along a longitudinal axis of the core sampler. In this aspect, the smaller diameter shoe portion can allow for an undisturbed sample, while the larger diameter tube portion can impart increased strength to the core sampler. In a further aspect, the larger diameter tube portion can provide the thickness needed for a liner, thereby permitting the core sampler to be reusable.

Referring now to the Figures, FIG. 1 illustrates a perspective view of an exemplary core sampler 10. FIGS. 2 and 3 illustrate cross-sectional views of the core sampler 10. As shown by FIGS. 1-3, in exemplary aspects, the core sampler 10 can include a shoe portion 12, a tube portion 14, and an adapter 16.

In one aspect, the tube portion 14 can be open at both a proximal end and an opposed distal end so that the interior may be occupied by a core sample introduced through the open distal end. In this aspect, the distal end of the tube portion can define one or more openings 21 for receiving the core sample. It is contemplated that the tube portion 14 can be constructed of any suitable material, such as, for example and without limitation, steel, a composite material, or other metal alloy that permits the tube portion 14 to withstand forces associated with drilling as described herein. It is further contemplated that the tube portion 14 can have a shape and size configured to allow for the housing of a core sample. In an exemplary aspect, as shown in FIGS. 1-3, the tube portion 14 can have a cylindrical shape with a substantially circular cross-section, and an inner surface of the tube portion can define a central bore 23 surrounding the longitudinal axis 50 of the core sampler and extending between the proximal and distal ends of the tube portion. One skilled in the art will appreciate that it is contemplated that the tube portion 14 can have various lengths and widths, depending on the desired size of the core sample.

In another aspect, the shoe portion 12 can be coupled or otherwise secured to the distal end of the tube portion 14. In this aspect, the shoe portion 12 can operate to facilitate penetration into a formation. In a further aspect, the shoe portion 12 can comprise a coring drill bit or other device capable of penetrating and capturing a core sample. In an exemplary aspect, as shown in FIGS. 1-3, the shoe portion 12 can have an annular shape with a distal end having a beveled or tapered portion 22. In this aspect, as shown in FIG. 5, it is contemplated that the beveled or tapered portion 22 of the distal end of the shoe portion 12 can have a taper 26 that is sufficiently sharp to facilitate penetration into a formation. It is further contemplated that the taper 26 can be about twenty degrees or less or optionally about fifteen degrees or less as measured relative to the longitudinal axis 50 of the core sampler 10 moving along the longitudinal axis 50 of the core sampler toward the opening 21 of the distal end of the shoe portion. In another aspect, as shown in FIG. 2, it is contemplated that an inner surface of the shoe portion 12 can define a central bore 25 surrounding the longitudinal axis 50 of the core sampler and extending between the proximal end and the distal end of the shoe portion.

It is contemplated that the shoe portion 12 can be operatively coupled to the tube portion 14 in any conventional manner, such as, for example, by welding, pins, clamps, threads, and the like. In an exemplary aspect, as shown in FIGS. 4 and 5, the tube portion 14 can comprise internal threads, and the shoe portion 12 can include external threads configured for complementary engagement with the internal threads of the tube portion 14. Alternatively, it is contemplated that the shoe portion 12 can be integrally formed with the tube portion 14.

In one aspect, as shown in FIG. 5, the shoe portion 12 can be thin-walled relative to the tube portion 14. More particularly, in another aspect, the shoe portion 12 can have an inner diameter 28 (defined by an inner surface of the shoe portion) and an outer diameter 30 (defined by an outer surface of the shoe portion). In this aspect, it is contemplated that the radial distance between the inner surface and the outer surface, i.e., the thickness of the shoe portion 12, can range from about 0.10 to about 0.20 inches; more preferably, can range from about 0.12 to about 0.15 inches, and, most preferably, can be about 0.14 inches. It is contemplated that the relatively small thickness of the walls of the shoe portion 12 can help prevent disturbance of a core sample and allow Class 1 samples (as defined by European Standard BS EN ISO 22457-1) to be obtained. In further aspects, the area ratio of the shoe portion 12 (or the outer diameter squared minus the inner diameter squared, divided by the inner diameter squared, times 100) can be less than about 25 percent, more preferably, can be less than about 20 percent, and, most preferably, can be less than about 15 percent.

In another aspect, as shown in FIG. 5, the tube portion 14 can be thicker than the shoe portion 12. In this aspect, the inner diameter of the tube portion 14 can be defined by an inner surface of the tube portion, and the maximum outer diameter 32 of the tube portion 14 (defined by an outer surface of the tube portion) can be larger than the outer diameter 30 of the shoe portion 12. It is further contemplated that the inner diameter of the tube portion 14 can be substantially equal to the inner diameter 28 of the shoe portion. In exemplary aspects, the thickness of the tube portion can correspond to the radial distance between the inner surface and the outer surface of the tube portion 14. It is further contemplated that the thicker gauge of the tube portion 14 can impart strength to the core sampler 10 and permits the core sampler 10 to withstand forces associated with sonic drilling and/or harder formations. As explained in greater detail below, it is further contemplated that the increased thickness of the tube portion 14 can provide space for a liner 18.

In an exemplary aspect, as shown in FIG. 5, the tube portion 14 can comprise a tapered portion 24 that transitions from the outer diameter 30 of the shoe portion 12 to the outer diameter 32 of the tube portion 14. In this aspect, the tapered portion 24 of the tube portion 14 can be inwardly tapered relative to the longitudinal axis 50 of the core sampler 10 moving along the longitudinal axis 50 of the core sampler toward the shoe portion 12. As explained in greater detail below, it is contemplated that the tapered portion 24 or transition to the thicker portion of the core sampler 10 can be spaced from the distal end of the shoe portion 12 so as to not disturb a core sample entering the core sampler 10 through the shoe portion 12.

In an additional aspect, it is contemplated that the combined thickness of the liner 18 and the tube portion 14 can be greater than the thickness of the shoe portion 12. For example, it is contemplated that the combined thickness of the liner 18 and the tube portion 14 can be about twice the thickness of the shoe portion 12. In exemplary aspects, the combined thickness of the liner 18 and the tube portion 14 can be between about 0.15 and about 0.50 inches or greater, more preferably, can be between about 0.20 and about 0.30 inches, and, most preferably, can be about 0.28 inches.

Optionally, as mentioned previously and as shown in FIGS. 2 and 3, the tube portion 14 can house a liner 18. In this aspect, the liner 18 can be positioned between the proximal end of the shoe portion 12 and the adapter 16. Thus, it is contemplated that the liner 18 can be sandwiched between the shoe portion 12 on the bottom and the adapter 16 on the top. It is contemplated that the replaceable liner 18 can allow for a core sample that complies with European Standard BS EN ISO 22457-1 and can permit the sampling tube portion 14 to be reused. In exemplary aspects, the liner 18 can be configured to fit into the honed smooth tube portion 14, which can permit the liner 18 to be inserted and extracted easily. Thus, it is contemplated that the core sampler 10 can allow for replaceable liners such that the more complex, costlier components (e.g., tubes) can be reused, and only the inexpensive components (e.g., liners) are consumed, yet still provide a compliant, undisturbed sample that satisfies European Standard BS EN ISO 22457-1.

In one aspect, the liner 18 can be configured to contain and protect the core sample. In this aspect, it is contemplated that the liner 18 can act as a consumable product that can be sent with a core sample, thereby allowing a driller to replace the liner 18 and use the core sampler 10 again. It is further contemplated that the liner 18 can assist in improving core recovery in certain soil types.

In an additional aspect, the liner 18 can have a shape and size that is configured to allow for the housing of a core sample. For example, as shown in FIGS. 2-3, it is contemplated that the liner 18 can have a substantially cylindrical shape with a substantially circular cross-section. One skilled in the art will appreciate that it is contemplated that the liner 18 can have various lengths and widths, depending on the desired size of the core sample and the size of the tube portion 14. In further aspects, the liner 18 can comprise various suitable materials. For example, it is contemplated that the liner 18 can comprise a polymeric material, a plastic material, and the like. In other exemplary aspects, it is contemplated that the liner 18 can comprise steel, a composite material, or other metal alloy. In another aspect, it is contemplated that the inside of the liner 18 can be substantially smooth with minimal or no protruding edges or irregularities, thereby reducing disturbance of a core sample.

In still another aspect, and with reference to FIGS. 1-3, the core sampler 10 can comprise an adapter 16. In this aspect, the adapter 16 can be configured to be operatively coupled to a drill rod or other drill string component. In exemplary aspects, the adapter 16 can comprise means for coupling to the drill rod or other drill string component. It is contemplated that the means for coupling can comprise, for example and without limitation, threads and/or another connection device, such as a pin (such as pin 34 of FIG. 6) or a locking ring, to affect such coupling.

In another aspect, the adapter 16 can house a check valve 20. In this aspect, it is contemplated that the check valve 20 can comprise a ball valve. In this aspect, it is contemplated that the check valve can be configured to allow the system to vent air out during sampling but create a vacuum on the sample to prevent sample loss when the core sampler 10 is extracted from the bore hole. It is further contemplated that the check valve 112 can be configured to allow fluid, gases, and other low density materials to exit tube portion 14 generally upwardly. In one exemplary aspect, during an exemplary drilling operation, it is contemplated that the borehole and tube portion 14 can be filled with fluid, and the check valve 20 can allow this fluid to exit the tube portion 14 without exerting constant downward or static hydraulic pressure on the interior of tube portion 14. Thus, it is contemplated that check valve 20 can provide any excess fluid with an escape path out of tube portion 14. Furthermore, by creating a vacuum, it is contemplated that the check valve 20 can help ensure that softer core samples (such as, for example, sandy core samples) do not fall out of the proximal end of the core sampler during extraction of the core sampler 10 from the bore hole.

In a further aspect, and with reference to FIG. 5, the tapered portion 24, where the core sampler 10 transitions from the smaller diameter of the shoe portion 12 to the larger diameter of the tube portion 14, can be offset from the distal end of the shoe portion 12. It is contemplated that, as the core sampler 10 is advanced into a selected geologic formation, the offset of the tapered portion 24 from the distal end of the shoe portion 12 can help ensure that, by the time the maximum-diameter portion of the tube portion 14 of the core sampler 10 contacts the formation and causes more significant soil disturbance, a core sample will be positioned inside the tube portion 14 in a desired comparatively undisturbed state.

In exemplary aspects, as shown in FIG. 6, the tapered portion 24 of the core sampler 10 can be positioned a first distance 36 from the distal end of the shoe portion 12. It is contemplated that the first distance 36 can be about 4 inches or more. However, it is also contemplated that, in some aspects, the first distance 36 can be less than about 4 inches. In an additional aspect, and with reference to FIG. 5, the first distance 36 can be at least as large as the inner diameter 28 of the shoe portion 12. In this aspect, it is contemplated that the first distance 36 can be between about 1.0 and about 2.0 times larger than the inner diameter 28 of the shoe portion 12. More preferably, it is contemplated that the first distance 36 can be between about 1.0 and about 1.5 times larger than the inner diameter 28 of the shoe portion 12. Most preferably, it is contemplated that the first distance 36 can be between about 1.20 and about 1.25 times larger than the inner diameter 28 of the shoe portion 12.

In another aspect, it is contemplated that the first distance 36 can have a selected ratio relative to the length 40 of the liner 18. In this aspect, it is contemplated that the first distance 36 can be between about 0.15 and about 0.40 times the length 40 of the liner 18. More preferably, it is contemplated that the first distance 36 can be between about 0.20 and about 0.30 times the length 40 of the liner 18. Most preferably, it is contemplated that the first distance 36 can be about 0.25 times the length 40 of the liner 18.

In an additional aspect, the first distance 36 can have a selected ratio relative to the distance 42 from the distal end of the shoe portion 12 to the proximal end of the liner 18. In this aspect, it is contemplated that the first distance 36 can be between about 0.10 and about 0.25 times the distance 42 from the distal end of the shoe portion 12 to the proximal end of the liner 18. More preferably, it is contemplated that the first distance 36 can be between about 0.15 and about 0.20 times the distance 42 from the distal end of the shoe portion 12 to the proximal end of the liner 18. Most preferably, it is contemplated that the first distance 36 can be about 0.18 times the distance 42 from the distal end of the shoe portion 12 to the proximal end of the liner 18. In various aspects, it is contemplated that the tapered portion 24 or point at which the core sampler 10 widens can be positioned at a distance 36 from the distal end of the shoe portion 12 sufficient to prevent disturbance of a core sample retrieved by the core sampler 10.

One will appreciate that the overall length 38 of the shoe portion 12 and the overall length 44 of the core sampler 10 can be varied as desired. For example, it is contemplated that the length of the various components of the core sampler 10 and/or the overall length 44 of the core sampler 10 can be varied based on drilling conditions and/or a desired core sample size.

In exemplary aspects, as shown in FIG. 7, a drilling system 100 can be used to retrieve a core sample from a formation 102. In these aspects, the drilling system 100 can comprise a drill string 104 that includes a core sampler 10 and one or more drill rods 108. As used herein, the terms “down” and “distal end” refer to the end of the drill string 104 that includes the core sampler 10. While the terms “up” or “proximal” refer to the end of the drill string 104, which is opposite the core sampler 10. Additionally, the terms “axial” or “axially” refer to the direction along the length of the drill string 104. In one aspect, it is contemplated that the longitudinal axis 50 of the core sampler 10 can be substantially axially aligned with the drill string 104.

In further aspects, the drilling system 100 can comprise a drill rig 114 that is configured to rotate and/or push the core sampler 10, the drill rods 108 and/or other portions of the drill string 104 into the formation 102. In these aspects, the drill rig 114 can comprise, for example, a drill head 116, a sled assembly 118, and a mast 120. In use, it is contemplated that the drill head 116 can be coupled to the drill string 104 and can permit the drill head 116 to rotate the core sampler 10, the drill rods 108 and/or other portions of the drill string 104. If desired, the drill head 116 can be configured to vary the speed and/or direction that it rotates these components. In one aspect, the sled assembly 118 can be configured to move relative to the mast 120. In this aspect, as the sled assembly 118 moves relative to the mast 120, the sled assembly 118 can provide a force against the rotary drill head 116. It is contemplated that the force against the rotary drill head 116 provided by the sled assembly in this fashion can push the core sampler 10, the drill rods 108 and/or other portions of the drill string 104 further into the formation 102.

It will be appreciated, however, that the drill rig 114 does not require a rotary drill head, a sled assembly, a slide frame or a drive assembly and that the drill rig 114 can comprise other suitable conventional components. It will also be appreciated that the drilling system 100 does not require a drill rig and that the drilling system 100 can comprise other suitable conventional components that can be configured to rotate and/or push the core sampler 10, the drill rods 108 and/or other portions of the drill string 104 into the formation 102. For example, it is contemplated that conventional sonic, percussive, or down hole hammers can be used.

In one exemplary aspect, the drill head 116 can comprise a sonic drill head. In this aspect, the sonic drill head can be configured to generate and transfer oscillating forces to the drill string 104 and core sampler 10 to urge the core sampler 10 into the formation 102. For example, it is contemplated that the sonic drill head 116 can include an oscillation assembly having an oscillator housing that supports eccentrically weighted rotors. It is further contemplated that the eccentrically weighted rotors can be configured to rotate within the oscillator housing to generate cyclical, oscillating centrifugal forces, which are then transferred to the drill string 104. It is still further contemplated that the increased thickness of the tube portion 14 can provide adequate strength to the core sampler 10 so as to permit the core sampler to withstand the relatively significant forces associated with sonic drilling.

In operation, the sonic drill head can oscillate and push (and optionally rotate) the core sampler 10 into the formation 102 to allow a core sample to be collected within core sampler 10. After the core sample is collected, the drill string 104 can be tripped from the borehole, and the core sampler 10 can be retrieved. The core sample can be removed from the core sampler 10 by removing the shoe portion 12 and removing the liner 18 with the core sample therein. After the core sample is removed, a new liner 18 can be positioned within the core sampler 10 and the shoe portion 12 reattached. The core sampler 10 can then be rotated and/or pushed further into the formation 102 to allow another core sample to be collected within the core sampler 10. The core sampler 10 can be repeatedly retrieved and sent back in this manner to obtain multiple core samples.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other aspects of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

1. A core sampler for advancement within a geologic formation to obtain a core sample, the core sampler having a longitudinal axis, the core sampler comprising: a shoe portion having an inner surface, an outer surface, a proximal end, and an opposed distal end, the inner surface of the shoe portion defining a central bore surrounding the longitudinal axis of the core sampler and extending between the proximal end and the distal end of the shoe portion, the distal end of the shoe portion defining an opening in communication with the central bore and configured to receive the core sample, the shoe portion having a thickness corresponding to the radial distance between the inner surface and the outer surface of the shoe portion, the distal end of the shoe portion comprising a tapered portion in which the outer surface of the shoe portion is inwardly tapered relative to the longitudinal axis of the core sampler moving along the longitudinal axis of the core sampler toward the opening of the distal end of the shoe portion; and a tube portion having an inner surface, an outer surface, a proximal end, and an opposed distal end, the distal end of the tube portion being secured to the proximal end of the shoe portion, the inner surface of the tube portion defining a central bore surrounding the longitudinal axis of the core sampler and extending between the proximal end and the distal end of the tube portion, the tube portion having a thickness corresponding to the radial distance between the inner surface and the outer surface of the tube portion, wherein the thickness of the tube portion is greater than the thickness of the shoe portion.
 2. The core sampler as recited in claim 1, further comprising a liner removably received within the central bore of the tube portion.
 3. The core sampler as recited in claim 1, wherein the shoe portion and the tube portion of the core sampler each have a substantially annular cross-sectional shape along the longitudinal axis of the core sampler, wherein the shoe portion has a maximum outer diameter defined by the outer surface of the shoe portion, wherein the tube portion has a maximum outer diameter defined by the outer surface of the tube portion, and wherein the maximum outer diameter of the tube portion is greater than the maximum outer diameter of the shoe portion.
 4. The core sampler as recited in claim 1, wherein the shoe portion and the tube portion of the core sampler each have a substantially annular cross-sectional shape along the longitudinal axis of the core sampler, wherein the shoe portion has an inner diameter defined by the inner surface of the shoe portion, wherein the tube portion has an inner diameter defined by the inner surface of the shoe portion, and wherein the inner diameter of the tube portion is substantially equal to the inner diameter of the shoe portion.
 5. The core sampler as recited in claim 1, wherein the distal end of the tube portion comprises a tapered portion in which the outer surface of the tube portion is inwardly tapered relative to the longitudinal axis of the core sampler moving along the longitudinal axis of the core sampler toward the shoe portion of the core sampler.
 6. The core sampler as recited in claim 1, wherein the tapered portion of the distal end of the shoe portion is inwardly tapered relative to the longitudinal axis of the core sampler at an angle of about fifteen degrees or less.
 7. The core sampler as recited in claim 2, wherein the liner has a radial thickness, and wherein the combined thickness of the liner and the tube portion is at least about twice the thickness of the shoe portion.
 8. The core sampler as recited in claim 5, wherein the shoe portion and the tube portion of the core sampler each have a substantially annular cross-sectional shape along the longitudinal axis of the core sampler, wherein the shoe portion has an inner diameter defined by the inner surface of the shoe portion, wherein the tapered portion of the distal end of the tube portion is spaced a selected distance from the distal end of the shoe portion, and wherein the selected distance by which the tapered portion of the distal end of the tube portion is spaced from the distal end of the shoe portion is between about 1.0 and about 2.0 times larger than the inner diameter of the shoe portion.
 9. The core sampler as recited in claim 1, further comprising an adapter coupled to the proximal end of the tube portion, wherein the adapter is configured for operative coupling to a drill string component.
 10. A core sampler for advancement within a geologic formation to obtain a core sample, the core sampler having a longitudinal axis, the core sampler comprising: a shoe portion having an inner surface, an outer surface, a proximal end, and an opposed distal end, the inner surface of the shoe portion defining a central bore surrounding the longitudinal axis of the core sampler and extending between the proximal end and the distal end of the shoe portion, the distal end of the shoe portion defining an opening in communication with the central bore and configured to receive the core sample, the shoe portion having a thickness corresponding to the radial distance between the inner surface and the outer surface of the shoe portion; a tube portion having an inner surface, an outer surface, a proximal end, and an opposed distal end, the distal end of the tube portion being secured to the proximal end of the shoe portion, the inner surface of the tube portion defining a central bore surrounding the longitudinal axis of the core sampler and extending between the proximal end and the distal end of the tube portion, the tube portion having a thickness corresponding to the radial distance between the inner surface and the outer surface of the tube portion, wherein the thickness of the tube portion is greater than the thickness of the shoe portion.
 11. The core sampler as recited in claim 10, further comprising a liner removably received within the central bore of the tube portion.
 12. The core sampler as recited in claim 10, wherein the shoe portion and the tube portion of the core sampler each have a substantially annular cross-sectional shape along the longitudinal axis of the core sampler, wherein the shoe portion has a maximum outer diameter defined by the outer surface of the shoe portion, wherein the tube portion has a maximum outer diameter defined by the outer surface of the tube portion, and wherein the maximum outer diameter of the tube portion is greater than the maximum outer diameter of the shoe portion.
 13. The core sampler as recited in claim 10, wherein the shoe portion and the tube portion of the core sampler each have a substantially annular cross-sectional shape along the longitudinal axis of the core sampler, wherein the shoe portion has an inner diameter defined by the inner surface of the shoe portion, wherein the tube portion has an inner diameter defined by the inner surface of the shoe portion, and wherein the inner diameter of the tube portion is substantially equal to the inner diameter of the shoe portion.
 14. The core sampler as recited in claim 10, wherein the distal end of the tube portion comprises a tapered portion in which the outer surface of the tube portion is inwardly tapered relative to the longitudinal axis of the core sampler moving along the longitudinal axis of the core sampler toward the shoe portion of the core sampler.
 15. The core sampler as recited in claim 10, wherein the distal end of the shoe portion comprises a tapered portion in which the outer surface of the shoe portion is inwardly tapered relative to the longitudinal axis of the core sampler moving along the longitudinal axis of the core sampler toward the opening of the distal end of the shoe portion.
 16. The core sampler as recited in claim 15, wherein the tapered portion of the distal end of the shoe portion is inwardly tapered relative to the longitudinal axis of the core sampler at an angle of about fifteen degrees or less.
 17. The core sampler as recited in claim 11, wherein the liner has a radial thickness, and wherein the combined thickness of the liner and the tube portion is at least about twice the thickness of the shoe portion.
 18. The core sampler as recited in claim 14, wherein the shoe portion and the tube portion of the core sampler each have a substantially annular cross-sectional shape along the longitudinal axis of the core sampler, wherein the shoe portion has an inner diameter defined by the inner surface of the shoe portion, wherein the tapered portion of the distal end of the tube portion is spaced a selected distance from the distal end of the shoe portion, and wherein the selected distance by which the tapered portion of the distal end of the tube portion is spaced from the distal end of the shoe portion is between about 1.0 and about 2.0 times larger than the inner diameter of the shoe portion.
 19. The core sampler as recited in claim 10, further comprising an adapter operatively coupled to the proximal end of the tube portion, wherein the adapter is configured for operative coupling to a drill string component.
 20. A core sampler for advancement within a geologic formation to obtain a core sample, the core sampler having a longitudinal axis, the core sampler comprising: a shoe portion having an inner surface, an outer surface, a proximal end, and an opposed distal end, the inner surface of the shoe portion defining a central bore surrounding the longitudinal axis of the core sampler and extending between the proximal end and the distal end of the shoe portion, the distal end of the shoe portion defining an opening in communication with the central bore and configured to receive the core sample, the shoe portion having a thickness corresponding to the radial distance between the inner surface and the outer surface of the shoe portion, the distal end of the shoe portion comprising a tapered portion in which the outer surface of the shoe portion is inwardly tapered relative to the longitudinal axis of the core sampler moving along the longitudinal axis of the core sampler toward the opening of the distal end of the shoe portion; a tube portion having an inner surface, an outer surface, a proximal end, and an opposed distal end, the distal end of the tube portion being secured to the proximal end of the shoe portion, the inner surface of the tube portion defining a central bore surrounding the longitudinal axis of the core sampler and extending between the proximal end and the distal end of the tube portion, the tube portion having a thickness corresponding to the radial distance between the inner surface and the outer surface of the tube portion; an adapter operatively coupled to the proximal end of the tube portion, wherein the adapter is configured for operative coupling to a drill string component; and a check valve positioned within the adapter and in operative communication with the central bore of the tube portion of the core sampler, wherein the thickness of the tube portion is greater than the thickness of the shoe portion. 